The present invention relates to a magnetic recording medium, a method of manufacturing the same, and an intermediate for the magnetic recording medium, and more particularly, to a magnetic recording medium having good magnetic reproducing characteristics without damaging a magnetic recording layer, and a method of manufacturing the same.
The significant enhancement in an areal density has been promoted for a magnetic recording medium such as a hard disk by using a means improving minuteness of magnetic particles constituting a magnetic recording layer, a change in a material, minuteness of head processing and so forth, so that a further enhanced areal density is expected in the future. However, the improving means employed up to the recent years faces limitation in enhancing the areal density because of problems of head processing limits, side fringe resulted from an enlarged magnetic field, crosstalk or the like, so that it is not possible to further enhance the areal density using the conventional means.
To cope with such a problem, a discrete track type magnetic recording medium has been proposed as one of means capable of enhancing an areal density of a magnetic recording medium, for example, see JP-A-9-97419 and JP-A-2000-195042. This discrete track type magnetic recording medium has a magnetic recording layer formed in a concentric track pattern, and a non-magnetic layer continuously filled within a concave portion between adjacent tracks in a track direction to separate the concentric track patterns.
In manufacturing the discrete track type magnetic recording medium, in order to suppress a flying deviation of a head slider with a magnetic bead mounted thereon, it is general to fill a concave portion between adjacent tracks formed in a concentric track pattern with a non-magnetic layer to flatten a top surface of the magnetic recording medium. A method of filling the concave portion between adjacent tracks with the non-magnetic layer employs a film formation technique such as sputtering utilized in a semiconductor fabrication field. According to such a film formation technique, the non-magnetic layer is formed not only between the tracks but also on a top surface of the magnetic recording layer, which causes to increase a gap length between the magnetic head flied over the magnetic recording medium by airflow and the magnetic recording layer constituting the magnetic recording medium when a thickness of the non-magnetic layer on the magnetic recording layer is as thick as about 10 nm as disclosed in JP-A-2000-195042 (that is, it causes to increase the spacing loss between the magnetic head and the magnetic recording layer), so that the detecting sensitivity is deteriorated or a foreign substance may be readily deposited thereon.
To cope with this problem, it is preferable to make thinner the non-magnetic layer formed on the magnetic recording layer while flattening its surface, and, for example, a dry etching method is employed for the flattening means.
However, in the above-described flattening using the dry etching method, it is difficult to control the etching speed, and the magnetic recording layer may be damaged by overetching. In addition, in a case in which the overetching is performed, it is likely to have a step between the magnetic recording layer and the non-magnetic layer filled in the concave portion between the tracks. As a result, it makes unstable the magnetic head flying above the resultant magnetic recording medium by airflow, so that it is likely to adversely affect the flying characteristics of the magnetic head.
Accordingly, it is required not to damage the magnetic recording layer as well as control a thickness of the non-magnetic layer formed on the magnetic recording layer so as to suppress deterioration of the magnetic recording and reproducing characteristics resulted from the large spacing loss between the magnetic head and the non-magnetic layer to the maximum.